1. Field of the Invention
The present invention generally relates to the management of the assignment of resources, particularly radio resources of mobile communications networks, like mobile telephony networks and wireless data networks, to entities requesting services from the network.
2. Description of Related Art
In the field of radio communications networks, several different technologies and several different standards coexist. The radio communications networks of the second generation (so-called “2G” networks, like those complying with the GSM—Global System for Mobile communications) standard, which nowadays are the most broadly deployed and are mostly suited for enabling voice communications, will in the coming years go more and more side by side with radio communications networks of new generation, such as third-generation (“3G”) networks (like those complying with the UMTS—Universal Mobile Telecommunications System—standard) and fourth-generation networks (still in the course of being standardized), designed for supporting, in addition to plain voice communications, data exchange and multimedia (e.g., video telephony, television broadcasting and similar) services, as well as broadband data communications networks of the Wireless LAN (WLAN) type.
A common approach in network deployment is not to completely replace 2G networks already in operation with new-generation networks, rather to integrate the different types of networks. The integration between radio communications networks of new generation with 2G networks is made possible by the fact that the new network standards are specifically defined in such a way as to enable the integration of different network standards. For example, in the 3GPP (Third Generation Partnership Project) specifications, that set forth the characteristics of the UMTS, several procedures are defined enabling the interoperation (“interworking”) with GSM networks (all the 3GPP specification documents cited in this description can be downloaded from the Internet site www.3GPP.org). In particular, in the 3GPP Technical Report (TR) 25.881 titled “Improvement of RRM across RNS and RNS/BSS, Release 5”, and in the 3GPP TR 25.891 titled “Improvement of RRM across RNS and RNS/BSS, Release 6” functional models and network architectures are defined where Common Radio Resource Management (CRRM) policies can be applied.
A known market trend is that of using, in certain geographic areas referred to as “hot spots”, WLAN technologies, so as to enable users that happen to be located in those areas to enjoy a broadband access to a number of data communications services like Internet access. WLAN technologies can also be integrated within a mobile telephony network, particularly in the access network segment. For this reason, interoperation mechanisms are also being defined that enable WLAN technologies (e.g., complying with the IEEE 802.11 family of standards, or with the ETSI standard known as HIPERLAN2) to interoperate with 3G mobile telephony networks so as to enable access to the transport network thereof. For example, the 3GPP TR 23.934, titled “3GPP system to Wireless Local Area Network (WLAN) interworking functional and architectural definition, Release 6” specifies the functional requirements to be satisfied by those network architectures that include IEEE 802.11 WLAN accesses in the UMTS network. Similarly, the ETSI TR 101.957, titled “Broadband Radio Access Networks (BRAN): HIPERLAN Type 2; Requirements and architectures for interworking between HIPERLAN/2 and 3rd generation cellular systems”, specifies the interoperation mechanisms of HIPERLAN2 WLANs with the UMTS network.
Radio communications systems integrating two or more Radio Access Technologies (RATs) are referred to as “multi-RAT” systems.
So-called “multi-mode” mobile telecommunications terminals are already available on the market (like cellular phones, palmtops, Personal Digital Assistants—PDAs—, peripheral cards for Personal Computers—PCs, etc.) which can connect to networks complying with different standards, like the GSM, the UMTS, IEEE 802.11b/g/a WLAN. For example, dual-mode mobile phones can work both in GSM and in UMTS systems.
Generally, CRRM policies are implemented by means of CRRM algorithms that run on specific network equipment, like for example the Radio Network Controllers (RNCs) of a UMTS network, or the Base Station Controllers (BSCs) of a GSM network, and that, upon receiving service requests from users, allocate them on the better pool of radio communications resources, depending on a number of factors like the nature of the requested service, the load status of the network at the time the service request is received, the overall radio resources available.
Several CRRM policies solutions have been proposed in the art.
For example, in the International applications WO 2005/101880 and WO 2005/101889, solutions are proposed to the problem of the decisions to be taken by the network as to which type of radio access is to be assigned to incoming service requests.
In S. J. Lincke, “Vertical handover policies for common radio resource management”, International Journal of Communication Systems, vol. 18, No. 6, pp. 527-543, an overview is presented of simulation studies on engineering traffic across wireless networks using “vertical handovers”. In that paper, by “vertical handovers” it is meant handovers between “component networks” of an integrated heterogeneous network comprising a GSM-900 network, a DCS-1800 network, a UMTS network, a WLAN; component networks are for example the GSM cells, the EDGE (Enhanced Data rate for GSM Evolution), the FDD (Frequency Division Duplexing) and the TDD (Time Division Duplexing) cells of the UMTS network, the IEEE 802-11 b hot-spots of the WLAN. Three types of vertical handovers are defined: cell-size switch (handover to a different cell size), technology switch (handover to a different air interface protocol technology), and base station mode switch (handover to a base station that will change its technology to carry the session). According to the author of the cited paper, an adaptive placement technique may rearrange sessions between RANs (Radio Access Networks) in order to serve hard-to-place sessions. The rearranging of sessions can be implemented using a substitution technique whereby flexible mobile terminals overflow to free capacity for arriving inflexible sessions, which cannot be carried by alternative RANs.